1. Field of the Invention
The present invention relates to a method and an apparatus for testing in a manufacturing process a plurality of magnetic head devices each having a magnetic head ford recording and reading used in a hard disk, for example. More particularly, the present invention relates to a method and an apparatus for testing a plurality of magnetic head devices, which can improve testing efficiency by testing a plurality of magnetic head devices Simultaneously.
2. Description of the Related Art
FIG. 9 is a perspective view showing a magnetic head device according to the prior art. The magnetic head device H is provided with a flexure 2 at an end of a load beam (supporting member) 1. A magnetic head 3 is supported through the flexure 2. The load beam 1 and the flexure 2 are flexible supporting members formed with a flat spring or the like. A mount board 4 is molded at a basal end of the load beam 1.
Recording and reading function portions 5 are provided in a trailing side end portion T of the magnetic head 3.
The magnetic head 3 levitates with a tilt attitude caused by a leading side end portion L, which receives air flow above a disk as a recording device when the disk turns and is lifted from a surface of the disk. When the disk stops, the magnetic head 3 touches on the disk.
The recording and reading function portions 5 of the magnetic head device H includes an MR type thin film reading element, which uses a magnetic resistance effect, as its reading function portion, and an inductive type thin film recording element as its recording function portion, for example.
The magnetic head device H is tested with respect to recording and reading characteristics after its assembly is completed.
FIG. 10 is a perspective view for describing a conventional method for testing the magnetic head device H according to the prior art.
A disk-shaped recording medium 12 is held on a driver 11 and is rotationally driven. The magnetic head device H is tested with respect to recording and reading characteristics on the recording medium 12 by causing the magnetic head 3 to perform recording/reading.
The conventional method for testing a magnetic head device shown in FIG. 10 has disadvantage that only one magnetic head can be tested at a time.
When the magnetic head device H is tested, a radial position from a center O of the recording medium 12 to a scanning region f the recording and reading function portions 5 (see FIG. 9) of the magnetic head 3 is set at a predetermined position for the test in order to have an equal recording/reading condition for the magnetic head device H.
For example, in FIG. 10, the scanning region of the recording and reading function portions 5 of the magnetic head 3 is positioned on a circumference of a radius r on the recording medium 12.
When a plurality of magnetic head devices are placed on arbitrary and different radial positions, various conditions of each of the magnetic head devices, such as a skew angle, relative traveling speed, and others for the recording medium 12 are varied. Consequently, each of the magnetic head devices cannot be tested under equal conditions.
Also, a plurality of magnetic head devices could be located such that a scanning region of recording and reading function portions of each of the magnetic heads is positioned on a circumference of a radius r on the recording medium 12. However, such a method cannot be adopted.
When recording/reading characteristics of the magnetic head device H is tested in FIG. 10, a test write signal is recorded by scanning on the circumference of the radius r on the recording medium 12 through the recording function portion of the magnetic head 3. Then, the test write signal is read by the reading function portion of the magnetic head 3 in order to analyze a waveform of a read signal and determine whether the recording/reading characteristics of the magnetic head device H reach to a quality standard of a certain product or not.
Therefore, while one magnetic head device is scanning and recording/reading on a circumference of a radius r on the recording medium 12 while another magnetic head device is scanning and recording/reading on the circumference of the radius r on the recording medium 12, a problem arises that each of the magnetic head devices cannot perform recording/reading with reliability. The magnetic head devices may be reading the write signals recorded of the other magnetic head devices. The magnetic head devices may over write the write signals recorded by other magnetic head devices.
The present invention is made for overcoming the above-described problem of the related art. It is an object of the present invention to provide a method and an apparatus for testing a magnetic head device, which can improve testing efficiency by testing a plurality of magnetic head devices simultaneously.
According to a first aspect of the present invention, a method for testing a plurality of magnetic head devices is provided. Each magnetic head device comprises a supporting member and a magnetic head having a recording function portion and a reading function portion at an end of the supporting member. The method the steps of placing the plurality of magnetic head devices on different scanning regions in the radial direction of a disk-shaped recording medium, each of scanning regions being slightly displaced from each other in the radial direction of the recording medium; turning the disk-shape recording medium to record a magnetic signal on the recording medium and to read the recorded magnetic signal through each of the plurality of magnetic head devices; and evaluating the plurality of magnetic head devices simultaneously through the read signal.
When the plurality of magnetic head devices are tested, each of the scanning region in the radial direction is predetermined. However, in a real test, tolerances in a certain range is allowed in the radial position.
Therefore, even when magnetic heads of the plurality of magnetic head devices are placed on the recording medium simultaneously, the scanning regions of the recording function portion and the reading function portion of each magnetic head may be held within a certain range of tolerances. Thus, various conditions such as a skew angle and relative traveling speed of the respective magnetic head devices for the recording medium can fall in the tolerance range. At the same time, all of the magnetic head devices placed on the recording medium simultaneously can be tested under virtually equal testing conditions. Therefore, the plurality of magnetic head devices can be tested simultaneously and accurately, which provides a much more efficient testing process for a plurality of magnetic head devices.
Further, while at least one magnetic head device among the plurality of magnetic head devices is performing a recording operation on the recording medium, it is preferable that other magnetic heads are adjusted to wait in order not to perform a reading operation.
When each of all the magnetic head devices placed on the recording medium simultaneously is allowed to record and read in arbitrary timing, a condition occurs where one magnetic head device is performing a recording operation while the, other magnetic head device is performing a reading operation.
In the condition where one magnetic head device is performing a recording operation while the other magnetic head device is performing a reading operation, a write signal output by the magnetic head device performing a recording operation is transmitted to the other magnetic head device performing a reading operation, which causes noise. That is, crosstalk occurs between the plurality of magnetic head devices.
According to the present invention, while at least one magnetic head device among the plurality of magnetic head devices is performing a recording operation on the recording medium, other magnetic head devices are adjusted to wait in order not to perform a reading operation. As a result, the crosstalk can be prevented, and the plurality of magnetic head devices can be evaluated simultaneously and accurately.
Alternatively, all the plurality of magnetic head devices may be adjusted to perform a recording operation simultaneously in synchronization with a same timing signal. Then all the plurality of magnetic head devices may be adjusted to read simultaneously in synchronization with a same timing signal, for example. It can also prevent causing crosstalk among the plurality of magnetic head devices. That is, the plurality of magnetic head devices can be evaluated simultaneously and accurately.
When a plurality of magnetic head devices are placed on the recording medium, a radial interval between scanning regions on the recording medium where the recording function portions and the reading function portions of the plurality of magnetic head devices scan is preferably set to be spaced at about 100 xcexcm or larger. Thus, it can prevent interference between each recording track formed on the recording medium by each of the plurality of magnetic head devices.
Further, a radial interval between the scanning regions where the recording function portions and the reading function portions of the plurality of magnetic head devices is preferably set within about 1% of a reference radius set in a radial middle of the plurality of scanning regions.
When a plurality of magnetic head devices are placed at different radial positions on the recording medium, various conditions of each of the magnetic head devices for the recording medium are varied such as a skew angle and a relative traveling speed.
However, if a radial interval between scanning regions of the recording medium where the recording function portions and the reading function portions of the plurality of magnetic head devices scan is set within about 1% of a reference radius set in a radial middle of the plurality of the scanning regions, the conditions such as a skew angle and a relative traveling speed can fall in the tolerance range for the test. As a result, each of the magnetic head devices clan be evaluated under virtually equal conditions.
It should be noted that the plurality of magnetic head devices may be located such that they are positioned on one straight line formed by each of their recording function portions and reading function portions, with passing through the center of the recording medium and extending radially. As a result, the evaluation can be performed with the skew angles of their respective magnetic head devices being equal.
Further, a holder to which a supporting member of the magnetic head device is mounted may be provided by two or more times of the number of magnetic head devices to be tested simultaneously. Then, while the plurality of magnetic head devices are being tested by turning the recording medium, exchanging magnetic head devices is preferably performed in the other holder which does not hold the magnetic head under test. That is, while the magnetic head devices are being exchanged, other magnetic head devices can be tested. Thus, the test of the magnetic head devices can be performed continuously, and its testing efficiency is improved.
An apparatus for testing a plurality of magnetic head devices according to a second aspect of the present invention includes a driver for turning a disk-shape recording medium for a test, a plurality of holders, each holding a supporting member of the magnetic head device having a magnetic head with a recording function portion and a reading function portion and the holding member for supporting it, and placing the plurality of magnetic head device on different scanning regions in the radial direction of the disk-shaped recording medium, each of the scanning regions being slightly displaced from each other in the radial direction of the recording medium, a write signal generator for generating and outputting a write signal to the recording function portion of the magnetic head, a controller for instructing the write signal generator to generate a write signal and instructing the reading function portion of the magnetic head to read a write signal, a timing generator for generating a timing signal for synchronization of recording and reading, and an analyzer for analyzing a read signal sent from the reading function portion of the magnetic head device to determine recording and reading characteristics of the magnetic head device. The controller instructs individual magnetic head devices to record/read alternately or simultaneously in synchronization with the timing signal.
It is preferable that the write signal generator, the controller and the analyzer are placed one each for one of the plurality of magnetic head devices facing onto the recording medium simultaneously. It is also preferable that a communication device is provided by which each of the controllers monitors other controllers such that the controller can instruct each of the magnetic head devices to perform recording/reading alternately or simultaneously.
Further, the controller can cause the individual magnetic head devices to record/read alternately. In that case, while at least one magnetic head device among the plurality of magnetic head devices placed on the recording medium simultaneously is performing a recording operation on the recording medium, the other magnetic head devices may be adjusted to wait in order not to perform a reading operation, for example.
Alternatively, the controller can cause the individual magnetic head devices to record/read simultaneously. In that case, all of the plurality of magnetic head devices placed on the recording medium simultaneously may be adjusted to perform a recording operation simultaneously in synchronization with a same timing signal, for example, and then, after the recording operation, to perform a reading operation simultaneously in synchronization with a same timing signal, for example.
Preferably, the position of the holder is set such that radial intervals of scanning regions where the recording function portions and the reading function portions of the plurality of magnetic head devices scan a recording medium are spaced 100 xcexcm or larger. It can prevent that recording tracks formed on the recording medium by each of the plurality of magnetic head devices interfere with each other.
Preferably, the position of the holder is set such that radial intervals of scanning regions where the recording function portions and the reading function portions of the plurality of magnetic head devices scan a recording medium are within about 1% of a reference radius set in a radial middle of the plurality of scanning regions.
When a plurality of magnetic head devices are placed at different radial positions on the recording medium, various conditions are varied such as a skew angle and relative traveling speed of each magnetic head for the recording medium.
However, when positions of holders are set such that radial intervals of scanning regions where the recording function portions and the reading function portions of the plurality of magnetic head devices scan a recording medium are within about 1% of a reference radius set in a radial middle of the plurality of scanning regions, the conditions such as the skew angle and the relative travelling speed can fall in the tolerance range for the test. Thus, each of the magnetic head devices can be tested under virtually equal conditions.
It should be noted that the plurality of magnetic head devices may be located such that they are positioned on one straight line formed by each of their recording function portions and reading function portions, with passing through the center of the recording medium and extending radially. As a result, the test can be performed with the skew angle of their respective magnetic head devices being equal.
Further, the holder may be provided by two or more times of the number of magnetic head devices to be tested simultaneously. Then, while the recording medium is being turned to test the plurality of magnetic head devices, exchanging the magnetic head devices may be preferably performed in the other holder, which does not hold the magnetic head under test. Thus, since the test does not have to be stopped for the exchange of the magnetic head devices, the test of the magnetic head devices can be performed continuously. Accordingly, the testing efficiency is improved.
According to the method and the apparatus for testing a plurality of magnetic head devices of the present invention described above, when a plurality of magnetic heads of the magnetic head devices are placed on the recording medium simultaneously and scanning regions of the recording medium in the radial direction fall in a certain range of tolerance, tests can be performed with conditions of the individual magnetic head devices, such as a skew angle and a relative traveling speed, for the recording medium being virtually equal.
Further, by adjusting the plurality of magnetic head devices to perform recording/reading alternately or simultaneously, a state can be avoided where one magnetic head device is performing a recording operation while the other magnetic head device is performing a reading operation.
As a result, a plurality of magnetic head devices can be tested simultaneously and accurately, which provides significantly efficient processes for testing magnetic head devices.